This application claims priority from Japanese Patent Application No. 10-202478 filed Jul. 17, 1998.
1. Field of the Invention
This invention relates to stock material for a container body of an insulating paper container having low melting point (m.p.) thermoplastic synthetic resin film laminated on the outer wall surface of said container body and expanded, the container and a process for making them.
2. Description of the Related Art
Japanese Patent Publication Gazette No. 1973-32283 describes the process comprising steps of laminating low m.p. thermoplastic synthetic resin film on at least one surface of moisture containing paper destined to become stock material for the container body and heating this film so that said film may be expanded to present an irregular surface under a pressure of water vapor discharged from said moisture containing paper constituting stock material. This literature describes also the technique such that the opposite surface of said paper is formed with a layer adapted to hold water vapor generated during the step of heating.
Japanese Patent Application Disclosure Gazette No. 1982-110439 describes, in regard to a paper container generally comprising the container body and the bottom wall, the process comprising steps of laminating low m.p. thermoplastic synthetic resin film on outer wall surface of said container body and heating this film so that said film may be expanded so as to present an irregular surface under a pressure of water vapor generated from moisture contained in the base paper. This literature describes also the technique such that a similar expandable thermoplastic synthetic resin film is laminated on the opposite surface of the base paper or this opposite surface is coated with aluminum foil so as to hold a pressure of water vapor generated during the step of heating.
Japanese Patent Application Disclosure Gazette No. 1993-42929 describes, in regard to the paper container generally comprising the container body and the bottom wall, the process comprising steps of doubly laminating low m.p. thermoplastic synthetic resin film and high m.p. thermoplastic synthetic resin film on outer wall surface of base paper of the container body and heating them so that only the low m.p. thermoplastic synthetic resin film forming the inner layer may be expanded and thereby the two-layered insulating paper container having the smooth and glossy outer layer. This literature described also the technique such that high m.p. thermoplastic synthetic resin film is laminated on the opposite surface of the base paper as a layer serving to hold a pressure of water vapor generated during heating treatment.
Japanese Patent Application Disclosure Gazette No. 1995-232774 describes, in regard to the paper container generally comprising the container body and the bottom wall, the process comprising steps of printing the base paper of the container body in a desired region on its outer wall surface with organic solvent containing ink, then laminating low m.p. thermoplastic synthetic resin film on said outer wall surface inclusive of the surface of said print, and heating this so that the printed region may be expanded more thickly than the remaining region to form the insulating paper container having locally different thickness. Description is also found in this literature that the step of printing may include a step of applying an anti-volatility layer in order to form an unexpanded region and a step of laminating high m.p. thermoplastic synthetic resin film on the opposite surface of the base paper.
Japanese Patent Application Disclosure Gazette No. 1997-95368 describes, in regard to the insulating paper container generally comprising the container body and the bottom wall, the process comprising steps of laminating low m.p. thermoplastic synthetic resin film on outer wall surface of the base paper for the container body applying desired region or regions on the upper surface of said film with synthetic resin ingredient containing coating and heating this so as to form expansion-inhibited region or regions corresponding to said region or regions on the outer surface of the container body applied with said synthetic resin ingredient containing coating.
Japanese Patent Application Disclosure Gazette No. 1997-142435 describes, in regard to the insulating paper container generally comprising the container body and the bottom wall, the process comprising steps of providing the outer wall surface of the base paper for the region or regions with printed layer, coating said printed region or regions with a layer of transparent varnish, laminating low m.p. thermoplastic synthetic resin film on the upper surface of said layer of transparent varnish and heating this film so as to achieve a uniform expansion and a satisfactory insulating property.
For every insulating paper container as disclosed in the above-identified documents, it is obviously essential to print various indications on the container body and particularly important to print the point-of-sale (POS) bar codes thereon so that they may be reliably read. In the case of such container having an expanded layer on the printed POS bar codes, said expanded layer often makes it to read the POS bar codes.
Especially for the case in which the POS bar codes are directly printed on the thermoplastic synthetic resin film laminated on the container body followed by expanding treatment, there is an apprehension that the printed bar codes might be deformed or distorted due to expansion of the film and reading of said POS might be adversely affected.
To solve this problem, Japanese Patent Application Disclosure Gazette No. 1995-232774 describes the countermeasure such that the outer wall surface of the base paper for the container body is formed with the expansile layer for printing and at the same time partially formed with the unexpanded region by coating said outer wall surface with the anti-volatility layer. Japanese Patent Application Disclosure Gazette No. 1997-95368 describes the countermeasure such that the upper surface of the low m.p. thermoplastic synthetic resin film laminated on the outer wall surface of the base paper for the container body is partially coated with the layer containing the expansion inhibiting synthetic resin followed by heating treatment in order to form an expansion inhibited region on the outer wall surface of the container body on which the POS bar codes may be distinctly printed. However, both the unexpanded region and the expansion inhibited region inevitably cause the corresponding recess to be formed on the outer surface of the container body which should be smooth. Such recess is undesirable from the viewpoint of the convenience for handling as well as of the aesthetic appearance. In addition, the insulating effect sufficient to ensure that the consumer can hold the container without any apprehension of getting burned on the hand cannot be expected in such unexpanded region and expansion inhibited region. Furthermore, the above-mentioned countermeasures of prior art result in unevenness of the insulating property.
In view of the problems as have been described above, the invention aims to provide stock material for the insulating paper container improved in its printability for bar codes or the like as well as in its insulating property, an improved process for making such stock material and an improved process for making the insulating paper container and the resulting containers.
The invention provides a process for making stock material for a container body of an insulating paper container, said process comprising steps of: laminating low m.p. thermoplastic synthetic resin film which is expandable by heating treatment on the outer wall surface of base paper as said stock material for the container body of the insulating paper container and applying the surface of said low m.p. thermoplastic resin film with compatibly expansile ink adapted to be expansile compatibly with expansion of said film.
The compatibly expansile ink is expansile in response to expansion of the low m.p. thermoplastic synthetic resin film without obstructing the expansion of said film. Accordingly, the low m.p. thermoplastic synthetic resin film to be expanded may be previously applied on its surface with said compatibly expansile ink to obtain a smooth printing surface substantially free from a touch of irregularity after said thermoplastic synthetic resin film has been expanded. In this way, POS bar codes or the like can be distinctly printed on the layer of said compatibly expansile ink.
In addition, the low m.p. thermoplastic synthetic resin film to be expanded may be previously applied on its surface with said compatibly expansile ink to prevent the printing ink from being soaked into the base paper and thereby to facilitate a recycling treatment of the base paper from the used insulating paper container according to this invention.
This invention provides a process further including a step of applying said surface of the low m.p. thermoplastic synthetic resin film which is expandable by the heating treatment with said compatibly expansile ink as a primer.
The property of said compatibly expansile ink allows the thermoplastic synthetic resin film to offer the smooth printing surface substantially free from a touch of irregularity after its expansion advantageously provides various possibilities. First, said compatibly expansile ink previously applied as primer on the entire surface of the thermoplastic synthetic resin to be expanded ensures the expanded resin surface to present an appearance as if it is the surface of the base paper itself. Upon such a surface, various objects can be printed in so-called false printing fashion, i.e., as if they are printed on the base paper""s background texture.
Secondly, the compatibly expansile ink is able to confine the water vapor generated from the low m.p. thermoplastic synthetic resin film during its expansion and thereby to promote the expansion rather than inhibiting it. As a result, the compatibly expansile ink is effective to increase a thickness of the expanded synthetic resin film without being affected by printing.
This invention also provides a process wherein the compatibly expansile ink applied as said primer is of white color. The compatibly expansile ink of white color may be applied on the resin film as primer to ensure that the surface of the expanded resin appears like the white background of paper and gives the paper container a good aesthetic appearance.
This invention provides a process further including a step of printing patterns, designs, letters, bar codes or the like on the surface of said compatibly expansile ink using separately prepared compatibly expansile ink.
In view of the advantageous property of the compatibly expansile ink allowing a smooth printing surface free from a touch of irregularity on the expanded thermoplastic synthetic resin, separately prepared ink of the similar property may be used to print patterns, designs, letters, bar codes or the like on such smooth printing surface to obtain a distinct image of POS bar codes or the like.
This invention provides the process according to any one of Claims 1-4, further including a step of at least partially filling an interface defined between the base paper and the low m.p. thermoplastic synthetic resin film with a layer of self-expansile ink.
The layer of self-expansile ink disposed between the base paper and the low m.p. thermoplastic synthetic resin film to be expanded improves an expansion effect as well as an insulating effect of the container. This is for the reason that not only expansion of said self-expansile ink correspondingly increases the thickness of the container body""s wall but also the region of the resin covered with said self-expansile ink is expanded with air bubbles of relatively large sizes and, thus, an advantageously thick layer of expansion is obtained. Accordingly, the interface defined between the base paper and the low m.p. thermoplastic synthetic resin film may be fully filled with the self-expansile ink and said effects may be correspondingly improved.
This invention also provides a process further including a step of laminating high m.p. thermoplastic synthetic resin film which is unexpanded even by heating treatment on the inner wall surface of the base paper as stock material for the container body.
The high m.p. thermoplastic synthetic resin film which is unexpanded even by heating treatment may be laminated on the inner wall surface of the stock material for the container body to block evaporation of moisture from said inner wall surface of the base paper, to promote expansion of the low m.p. thermoplastic synthetic resin film on the outer wall surface of the base paper and to ensure a sealability of the container after heating treatment.
This invention provides a process wherein the low m.p. thermoplastic synthetic resin film which is expandable by heating treatment is made of low density polyethylene having a MFR (melt flow rate) of 8-15 g/10 min and a thickness of 0.03-0.07 mm.
The low density polyethylene having a MFR (melt flow rate) of 8-15/10 min and a thickness of 0.03-0.07 mm may be used as the low m.p. thermoplastic synthetic resin film to facilitate the step of lamination on the base paper and to ensure that the compatibly expansile ink may follow expansion of said low density polyethylene and thereby may cover the expanded surface in the form of a smooth printing surface.
This invention provides a process wherein the high m.p. thermoplastic synthetic resin film which is unexpanded even by heating treatment is made of medium density polyethylene having a MFR (melt flow rate) of 4-8/10 min.
The medium density polyethylene having a MFR (melt flow rate) of 4-8 g/10 min may be used as the high m.p. thermoplastic synthetic resin film to facilitate the step of lamination on the base paper and to ensure a high sealability of the container after heating treatment.
This invention also provides a process wherein the base paper is obtained by the fortlinear paper machine or the cylinder paper machine.
Paper of a high air-permeability obtained by the fortlinear paper machine or the cylinder paper machine may be used as the base paper to obtain many advantageous properties including appropriate thickness and strength, high workability for lamination, high workability for assembling the container, high moisture content and high vaporability. These properties are effective to improve the expanding effect.
This invention provides also stock material for a container body of an insulating paper container, said stock material comprising: base paper; high m.p. thermoplastic synthetic resin film laminated on the inner wall surface of said base paper; low m.p. thermoplastic synthetic resin film laminated on the outer wall surface of said base paper wherein said low m.p. thermoplastic synthetic resin film is expandable by heating treatment; and compatibly expansile ink applied on the upper surface of said low m.p. thermoplastic synthetic resin film.
This invention provides stock material wherein said compatibly expansile ink is applied on upper surface of the low m.p. thermoplastic synthetic resin film which is expandable by heating treatment as primer.
This invention provides stock material wherein said compatibly expansile ink applied as said primer is of white color.
This invention provides stock material wherein the upper surface of said compatibly expansile ink is printed with patterns, designs, letters, bar codes or the like using separately prepared compatibly expansile ink.
This invention provides stock material wherein an interface defined between the base paper and the low m.p. thermoplastic synthetic resin film is at least partially filled with a layer of self-expansile ink.
This invention provides stock material wherein the low m.p. thermoplastic synthetic resin film which is expandable by heating treatment is made of low density polyethylene having a MFR (melt f low rate) of 8-15 g/10 min and a thickness of 0.03-0.07 mm.
This invention provides stock material wherein the high m.p. thermoplastic synthetic resin film which is unexpanded even by heating treatment is made of medium density polyethylene having a MFR (melt flow rate) of 4-8 g/10 min.
This invention provides also an insulating paper container generally comprising a container body and a bottom wall, said insulating paper container further comprising: high m.p. thermoplastic synthetic resin film laminated on the inner wall surface of base paper for said container body and bottom wall; low m.p. thermoplastic synthetic resin film laminated on the outer wall surface of the base paper for said container body; compatibly expansile ink applied on the upper surface of said low m.p. thermoplastic synthetic resin film so that said ink may follow expansion of said low m.p. thermoplastic synthetic resin film; and said low m.p. thermoplastic synthetic resin film being expanded by subjecting the lamination to heating treatment.
This invention provides an insulating paper container wherein the upper surface of the low m.p. thermoplastic synthetic resin film which is expandable by heating treatment is applied with said compatibly expansile ink as primer.
This invention provides an insulating paper container wherein said compatibly expansile ink applied as said primer is of white color.
This invention provides an insulating paper container wherein the upper surface of said compatibly expansile ink is printed with patterns, designs, letters, bar codes or the like using separately prepared compatibly expansile ink.
This invention provides an insulating paper container wherein an interface defined between the base paper and the low m.p. thermoplastic synthetic resin film is at least partially filled with self-expansile ink.
This invention provides an insulating paper container wherein the low m.p. thermoplastic synthetic resin film is laminated on the outer wall surface of the base paper for the bottom wall and said low m.p. thermoplastic synthetic resin film is expanded by subjecting the lamination to heating treatment.
In the case of the container like a bowl which is relatively large in its diameter and relatively small in its height, the consumer""s hand may sometimes come in contact with the bottom of such container. The apprehension that the consumer might get burned on the hand can be effectively avoided by coating the outer wall surface of the stock material for the bottom wall with the expanded insulating layer.
This invention provides an insulating paper container wherein the low m.p. thermoplastic synthetic resin film is laminated on the upper surface of the high m.p. thermoplastic synthetic resin film which is unexpanded even by heating treatment, said high m.p. thermoplastic synthetic resin film, in turn, being laminated on the inner wall surface of the base paper for the bottom wall of the insulating paper container, and the low m.p. thermoplastic synthetic resin film laminated on the base paper for the container body of the insulating paper container is expanded by subjecting the lamination to heating treatment.
The low m.p. thermoplastic synthetic resin film may be laminated on the surface of the high m.p. thermoplastic synthetic resin film which is, in turn, laminated on the inner wall surface of the base paper used as the stock material for the bottom wall not only to improve the insulating property of the bottom wall but also to ensure a high sealability on the inner wall surface of the container. Such high sealability is obtained for the reason that the high m.p. thermoplastic synthetic resin film laminated on the inner wall surface of the base paper used as the stock material for the container body is firmly heat-sealed with the low m.p. thermoplastic synthetic resin film on the inner wall surface of the bottom wall.
This invention provides an insulating paper container wherein the low m.p. thermoplastic synthetic resin film which is expandable by heating treatment is made of low density polyethylene having a MFR (melt flow rate) of 8-15 g/10 min and a thickness of 3-0.07 mm.
This invention provides an insulating paper container wherein the high m.p. thermoplastic synthetic resin film which is unexpanded even by heating treatment is made of medium density polyethylene having a MFR (melt flow rate) of 4-8 g/10 min.
This invention provides an insulating paper container wherein the base paper has a basis weight of 150-350 g/m2 and a moisture content of 5-9%.
In view of desired strength and workability of the base paper as well as desired expansion ratio and post-expansion insulating property of the laminated thermoplastic synthetic resin, the base paper preferably has a basis weight of 150-350 g/m2 and a moisture content of 5-9%.
This invention provides an insulating paper container wherein the base paper is product obtained by the fortlinear paper machine or the cylinder paper machine.
This invention provides also a process for making an insulating paper container generally comprising a container body and a bottom wall, said process comprising steps of: laminating high m.p. thermoplastic synthetic resin film on the inner wall surface of base paper for said container body and bottom wall; laminating low m.p. thermoplastic synthetic resin film on the outer wall surface of the base paper for said container body; applying the upper surface of said low m.p. thermoplastic synthetic resin film with compatibly expansile ink so that said ink may follow expansion of said low m.p. thermoplastic synthetic resin film and after the container has been formed by said container body and bottom wall, expanding said low m.p. thermoplastic synthetic resin film by subjecting the lamination to heating treatment.
This invention provides a process further including a step of applying the surface of said low m.p. thermoplastic synthetic resin film to be expanded by heating treatment with said compatibly expansile ink as primer.
This invention provides a process wherein said compatibly expansile ink applied as said primer is of white color.
This invention provides a process further including a step of printing the upper surface of said compatibly expansile ink with patterns, designs, letters, bar codes or the like using separately prepared compatibly expansile ink.
This invention provides a process further including a step of at least partially filling an interface defined between the base paper and the low m.p. thermoplastic synthetic resin film with a layer of self-expansile ink.
This invention provides a process further including steps of laminating the low m.p. thermoplastic synthetic resin film on the outer wall surface of the base paper for the bottom wall and expanding said low m.p. thermoplastic synthetic resin film by subjecting the lamination to heating treatment.
This invention provides a process further including steps of laminating the low m.p. thermoplastic synthetic resin film on the high m.p. thermoplastic synthetic resin film which is unexpanded even by heating treatment and laminated on the inner wall surface of the base paper for the bottom wall of the insulating paper container and expanding the low m.p. thermoplastic synthetic resin film associated with the container body by subjecting the lamination to heating treatment.
This invention provides a process wherein the low m.p. thermoplastic synthetic resin film which is expandable by heating treatment and constitutes the stock material for the container body of the insulating paper container is made of low density polyethylene having a MFR (melt flow rate) of 8-15 g/10 min and a thickness of 0.03-0.07 mm.
This invention provides a process wherein the high m.p. thermoplastic synthetic resin film which is unexpanded even by heating treatment is made of medium density polyethylene having a MFR (melt flow rate) of 4-8 g/10 min.
This invention provides a process wherein the heating treatment is carried out at a temperature of 120-130xc2x0 C. for 2-4 min.
The heating treatment may be carried out at a temperature of 12-130xc2x0 C. for 2-4 minutes to ensure that the low m.p. thermoplastic synthetic resin film laminated on the outer wall surface of the base paper can be sufficiently expanded.
These and other features, objects and advantages of the present invention will become apparent upon reading the following description thereof together with reference to the accompanying drawings.